A transitive godan verb meaning to fail to do something, to miss or botch (an action or opportunity) — to be unable to carry out or to miss doing what should have been done.
寝坊して電車に乗りそこなった。
I overslept and missed the train.
大事なチャンスを逃してしまい、やりそこなったと後悔している。
I missed an important chance and regret having failed to do it.
書類の重要な部分を読みそこなって、誤解が生じた。
I missed an important part of the document and a misunderstanding occurred.